Lith says the truth to Emilia and Alexandra
Lith looked at his ladies and explained to them that his mother and sister were his partners and that was the thing he had forgotten to share with Emilia and Alexandra.
He knew he shouldn't hide such things for long as it would only bite him in the ass later if he did that.
Just as he finished speaking, Emilia and Alexandra were a bit shocked to know this. The reason wasn't that Lith had his mother and sister as his partners but rather, the shock came from the fact that the revered Vampire Queen was in an incestous relationship with her own son.
Emilia and Alexandra both knew about Lilith's terror. Emilia was there when it was happening and even though Alexandra wasn't there, she had heard tales of it from her parents and clan members. It thus came as a shock when they realized this fact.